Depravity
by iguessso12
Summary: A Transcendence AU fic (for an AU of the TAU known as the Drift AU). One-shot. Summary: The years of Mabel's life march by. She has changed. Her brother has changed even more. Nowadays, Dipper is more demon than human.


Depravity

* * *

When Mabel was twelve, going on thirteen, the world ended. Her brother went up in blue flames. Not even ashes remained. Her parents came to get her. Told her she'd never return to Gravity Falls.

But the world didn't end. It changed. They called it The Transcendence.

* * *

"Dipper!" Mabel called, wiping her hands on a dish towel. The casserole was in the oven. She'd done up the dishes. It would be another half hour before it was ready to eat. That gave her a half hour to find her brother since he wasn't within hearing range. She wasn't feeling up to summoning him. It would be too messy.

He had checked in with her less than an hour ago. She somehow knew that he was still in Gravity Falls. Over their link there was an intensity that was only present when he was nearby. He was entertaining himself, that much was clear.

"Henry." She peeked in on her husband. He was fully focused on restoring an old book, glue, paper, and thread littered about his usually neat workspace.

"Yeah, Mabes?" He tossed her a glance and a warm smile, "What's up?"

"I set the alarm on the stove. Can you take the food out when it's done? I'm going to find Dipper. He's out in the woods somewhere."

"Yeah, no problem."

"Where are the kids?"

"Stan's with them. They're in the attic. I believe they're going through some of Stan and Ford's old things. Spring cleaning."

Mabel giggled, "That should keep them busy. One time, Stan told me and Dipper he'd get rid of a body switching rug we discovered in the Shack. We found it, later that summer, stuffed in a corner of the attic."

Henry went back to his book, but you could tell the smile remained on his face, "Stan's sentimental, even if he doesn't want to admit it. But that attic needs cleaned. The kids are getting bigger and they're going to need more space."

"I've been thinking about making a deal with Dipper to fix that." Mabel confessed.

She didn't miss the way her husband's back went rigid. To anyone else, it would be unnoticeable. But she knew Henry by heart. Every movement, every expression, every detail. She knew that there were still things about his brother-in-law that made Henry uneasy. With good reason.

"Are you sure, Mabes?"

"I'm always sure."

"But you've thought it out. Everything?"

Mabel nodded.

Henry deliberately continued with his book, moving steady hands over the delicate pages. A swath of glue affixed a new spine, held fast by a clamp while it dried. He reached for the next book, starting with the frayed stitching in the binding. Long, spindly fingers expertly threaded a needle.

"I trust you." He whispered quietly.

Mabel crossed the office, draping her arms around his neck so they dangled over his chest. He was the perfect height, sitting down. She rested her head on his shoulder.

"And I trust Dipper." She whispered back.

"I know."

"There's nothing wrong with that. It works for us."

"I know."

* * *

When Mabel was fourteen, the house in Piedmont was too small for three people. Her room, even though the attic was the first one they had shared, was too large. But the space wasn't just her own. Things moved when she wasn't looking. Her television fizzed out at odd moments. The temperature was always ten degrees colder than the rest of the house.

Salt and iron did nothing to make it stop. It wasn't a ghost.

* * *

Mabel grabbed her bat, grappling hook, and squirt bottle of anointed water on her way out of the house. Shack. Whatever. While the world was a much more dangerous place than it had been when she was twelve, she was well prepared for it at this point. Not that many magical creatures would try anything with her. Not when she belonged to someone – something – else.

The days were getting longer. The triplets had just finished first grade a few days ago. Summer was fast approaching. She was looking forward to it.

Humming a tune as she navigated the undergrowth, she found a well-beaten path. All around her, pine trees towered into the burning twilight of the sky. Their scent wafted on the fresh breeze, bringing back memories as scents often do. Back then, she couldn't have imagined things would be the way they were now. Or how much it would cost to get there.

Memories were peppered with pain and triumph, often at the expense of others. Expense and sacrifice. She knew too much about sacrifice. The world did not abide by the golden rule.

"Dipper!" She called.

He didn't answer. But she knew she was getting closer. It wasn't just twin intuition. It was a link, more explicit and inexplicable than could ever be understood by any other pair. After all, how often did a demon retain a soul rather than consume it whole?

Mabel braced her knees, arms out, as she slid down an incline layered in moss. The trees around her sparkled. There were unnatural hues to the plant life. She would think it beautiful, if it weren't so familiar.

"Dipper!"

A puff of black smoke and acrid sulfur was all the warning she received before luminescent, gold eyes hung in her vision. The rest of her brother resolved into focus. Face blooming in a smile with jagged teeth and inky suit sucking the light from the clearing.

 **"Ah, Mizar! You have perfect timing."**

"What's up Dip?" She'd had years to adjust to her brother's preference for her demon title rather than her real name. The sting was nothing but a dull ache, easily ignored.

An invisible wind ruffled Dipper's hair as he floated above her. A self-satisfied smirk fell into place. Eyes that conveyed nothing but joy and chaos alit with streams of gold as he whirled about to lead the way.

 **"You'll just have to come see!"**

She fell into step with his pace. Dipper reclined on his back. After all these years, he'd never once submitted to gravity. The day the portal had upset the laws of the nature was the day Dipper became everything that went against them. Absently, her brother picked something from his teeth that looked like white cotton candy.

* * *

When Mabel was fifteen, the school system finally got its act together and introduced a Transcendence Adjustment course. At Piedmont High, they received a brief overview of every known supernatural creature. Surprisingly, there was a section on demons.

Bill Cipher was common knowledge. He was gone. But another had taken his place. Alcor the Dreambender.

* * *

The gnomes were right were Mabel expected them to be, in their hidden cove. But finding them, standing, heaving with exertion, in full battle mode, was unexpected.

"What's going on, Dipper?" She queried.

Her brother's canny eyes glittered, half-lidded.

The gnome giant quivered.

 **"Gnomes are such a nuisance."** Dipper scoffed, **"The have a two-track mind. Food and finding a queen. When I made a little deal with them that they couldn't hold up, there needed to be something to settle the debt. And I was in the mood for a snack."**

Mabel finally noticed the gaping hole that was the gnome giant's left arm. No little men were scrambling to replace it. How many would it take? Fifty? One hundred?

Dipper grinned again, and the white fluff was easily identifiable as beard hair. The usually multicolored forest was even more colorful, painted by rainbow splatters of the innards of too many gnomes. Stagnant air was choked with the scent of spoiled lemons. She didn't know what gnome blood smelled like before. Now she did.

 **"Remember,"** Dipper's voice purred with pleasure, **"Something similar happened last week. That cult didn't really have anything equivalent to afford them control of this continent. Though I do admire how they aim low. How many have asked for control of this planet? Too many. Pure folly."**

She knew he would go on, so she reached up and grabbed his bow tie. For a brief moment, Dipper's eyes swirled with rage. He wasn't fond of touching. He wasn't fond of a gesture that presumed others were above him. He wasn't fond of anyone, save her.

Dipper had fought, tooth and nail, from his inception. Demons dogged his footsteps, hoping to feast on a new born for an extra boost of energy. Invisible and unheard, he trekked through the world. Tore apart his foes. And grew. Eyes that burned. Fangs so sharp. Claws for fingertips. Wings with power.

Viciousness that rivaled and rose above all others. Every summons was devoutly twisted to afford him the most advantage. The demon of before whispered into a corrupted human mind, creating a new demon. Cleverer. More devious. With another goal. Existing on the mortal plane of his own volition. Reclaiming his sister.

His sister. She was his sister. His twin. And her soul was his.

It was the only reason he didn't rip her apart for such a gesture. Another tug on his bow tie erased the anger, leaving only irritation.

 **"What?"**

* * *

When Mabel was sixteen, her parents finally hired an exorcist. The centaur shaman had managed to climb the steps to her room with his equine body. But when the crystals informed him of measurements the Pines family couldn't understand, the only thing they understood was his pale face and his quick retreat.

That night, a voice whispered, **"There is no use trying to keep me away."** Alcor tore his way through dimensions and into her life.

* * *

"Alcor." Mabel admonished. Dipper liked his title. It would get through to him with more force. Internally, she struggled. Sometimes she felt he was too far gone. Why would he even ask her to do this?

 **"What?"**

"This is unnecessary and you know it. The gnomes are harmless. They aren't a threat to anyone. Not like that cult at all."

 **"So?"**

"You asked me to find your humanity." She stabbed a finger at the wounded gnome giant, "How is this human? How is this even fair?"

The demon bristled, blue sparks jumping over his suit.

 **"I am Alcor. I do not descend to the level of humans and their pathetic interpretations of fairness."** A smile tore its way across his face. Irises blew wide and golden. Energy warped the atmosphere around him, shimmering like the heat over a highway. Sapphire fire pooled in his palms. **"I take what I see fit. And I see no problem with the souls of eighty-five gnomes. I feel fantastic. Would you like a taste, Mizar?"**

When Dipper got bored, he reminded the world who he was. With his title came power and prestige. Years with the ability to maintain corporeality never satiated his need for chaos. His title was to be feared and revered. The intelligent, curious, and dorky twelve year old boy was replaced by a creature that deemed to keep his human form. Memories of his humanity were scattered with his sanity.

Her brother came back. But he didn't. This creature was wearing his skin. He wasn't Dipper Pines. Wasn't Bill Cipher. He was Alcor the Dreambender. But even that was nothing more than another charade.

Mabel wasn't sure what Dipper was. But Dipper was her brother. She'd fight, tooth and nail, for him. To keep him by her side. To keep him from growing any more demonic while she was alive.

Intentionally overlooking the proffered hand, she answered, "When Forrest asks you to do his homework for him in exchange for his Halloween candy, what have I told you to do?"

Dipper's brow pinched together. **"Ignore his deal and explain the consequences of such a thing."**

"Exactly."

 **"How is this the same?"**

"Because Forrest is too young to understand and gnomes are too dense to know any better."

 **"Gnomes are delicious."**

"So is the casserole that is about to come out of the oven right now. If you aren't too full already, you can join us."

Dipper's bared his fangs.

 **"I'm never full."**

His hand still hung between them. He gave it a shake for emphasis.

"Conditions." Mabel admonished, "You mention none of this to the triplets. You behave yourself around them. And you help Henry with dishes."

 **"A plate of food isn't enough for that, Mizar."**

* * *

When Mabel was seventeen, she drove through night, blurred eyes, and heavy rain to Gravity Falls. All her belongings were packed into the trunk of her rickety Volkswagen beetle. Her phone rang thirty times before she simply turned it off. There was no going back.

Dipper had driven mom into an anxiety attack. Dad wanted to give the government information that would allow them to magically enslave him. She couldn't love them all at once.

* * *

"Seconds and thirds. Or no deal. I will leave you in these woods."

A flash of something. Concern writ across Dipper's face, choking the grin. She watched with interest. It was moments like these that she looked for. For her brother. The real thing.

Pushing his buttons. Trial and error. An elaborate guessing game. That's what it took to find her brother. To truly see what he had been through. Because he told her nothing. She needed to understand the war in his head. She needed to know how his natures dueled inside him. She needed to comprehend the clash of instincts and what he chose to act upon.

Why?

One moment he could be cradling baby Willow in his arms, cooing and watching over her with lamplight eyes. And the next he could snap and order a three-year-old Acacia by her true name to stab forks in her arm. He could grin as he and Forrest battled over a Snicker bar with a game of Super Smash Bros. But on Willow's first day of school, he thought showing her how the next ten years of her life played out was educational.

Every time she thought he was getting better, he'd backtrack twice as far.

 **"Deal!"**

Dipper didn't give her any more time to contemplate. He nabbed her arm, unaware of how his claws dug through the sleeve of her sweater and punctured her skin. He warped them into the Shack. Just in time for the oven to ding. She scrubbed warm rivulets of blood off with the inside of her sleeve and slid on oven mitts. Dipper hung around behind her.

She batted his hand away with the spatula.

Something must have clicked within his demon mind. Dishes, glasses, and silverware floated out of cabinets and rested on the table. All the while, Dipper floated in circles around the kitchen, on his back. Unconcerned and eyes closed, he missed out on the fond smile Mabel shot his way.

Henry had been summoned to the kitchen by the sound of the timer. A raised eyebrow at his wife and his brother-in-law was the only indicator that he was surprised. He most likely heard the blip upon their entrance. The triplets certainly did.

They tromped down the old wooden staircase, Stan following at a more relaxed pace. Pretty soon, the kitchen was packed with the members of their family. Three, red-headed children jumped up to nab their uncle's coat-tails as he had seemingly dozed off.

"Uncle Dipper?" Forrest asked, "Did you fall asleep?"

A puff of air replaced his floating form, and Dipper appeared to be lounging at the kitchen table. The triplets were left spinning in dizzy circles. Acacia fell on her butt.

 **"Why would a dream demon need to sleep?"**

Willow recovered the quickest, running to throw herself in his lap.

"We've seen you fall asleep before." Forrest reminded them all, not impressed.

* * *

When Mabel was eighteen, she earned her demon title: Mizar. Whether she was possessed or acted of her own volition, she learned of the havoc wrought by a demon. It forever changed her perspective of humanity. To know that there were people doing things just as depraved as demons chilled her to the bone.

She grew vicious to match her brother. Hiding the way it rotted her insides with a smile. Scars littered her skin and her soul.

* * *

Dinner was the same as ever. Delicious, loud, and a little bit crazy. The triplets told Dipper what they'd been up to all afternoon. Mabel found herself laughing at all the nostalgia they'd uncovered. Boxes of old video tapes were sitting in the living room, waiting to be watched after the meal. No doubt there were copies of 'Dipper's Guide to the Unexplained' and 'Mabel's Guide to Everything' among them.

When they had first moved into the Mystery Shack with Stan, she had watched them with Dipper to see what he remembered. It was strange to find that every scene, he could perfectly recall. But he regarded his past self with upmost contempt. **'It's funny how dumb I was.'**

She didn't mind the triplets watching the videos. But it would certainly be hard for her and Henry. They understood just what had happened to Dipper. To make him the way he was now. It was pretty messed up if they really thought about it.

The triplets were old enough to understand. Mabel and Henry had never hidden things from them. It was in their best interests to know, after all. Risk-taking was not permissible with a demon around.

They knew that their uncle had once been human. That he was a demon now. They knew that their uncle had dangerous mood swings. That happy wasn't always good and anger wasn't always their fault. They knew not to make deals with him without parental supervision. That the fact he knew their true names was a serious matter.

But sometimes, the triplets were just six. And sometimes rules slipped their minds or were disregarded. Sometimes the triplets and Dipper had terrible lapses in judgement at the same time. And the kids got hurt. Henry would grow silent. Mabel would race to right the mess as much as she could.

But fractures, while they can be repaired, are never really whole again.

Their family sat around the old tube television anyway. Slid the tapes into the dated VHS player. And pressed play on the console. They laughed about the past. Dipper added commentary with facts about the recording and the creatures he'd tried to identify at age twelve, all free of charge.

Willow cuddled in his lap. Acacia stole his hat. And Forrest asked more questions.

Henry and Mabel sat on the couch with fingers intertwined. She could feel his contentment as her head rested on his shoulder. Her husband just wanted his family to be safe, including his often wayward brother. But when the conflict came from within, he wasn't sure how to deal with it besides exercising saint-like patience. Mabel only loved him more for that. Dipper needed someone to approach him in a way his demon instincts didn't understand. Only that would get through to him.

Stan grouched about how lovey-dovey everyone was getting and went to bed. He was too old to put up with it.

* * *

When Mabel was nineteen, she almost gave up on Dipper. He'd disappeared for six months before blipping in to drag her off to a cult bust. It had been worse than anything she'd ever seen before. So much blood. Everywhere. His laugh as he tore people apart in the most slow, brutal, and painful way possible. His eyes, so bright with excess energy they seemed white.

She stood off to the side and watched. And vomited. And didn't eat or sleep for a week after. How could that still be her brother?

* * *

After everyone else had gone to bed, Mabel and Dipper lounged on the roof of the Shack. Times like these, Mabel felt no different than when she was a kid. Just the two of them, sneaking out to drink Pitt Cola past bedtime, throw pinecones at the totem pole, and watch the stars they couldn't see from Piedmont. Only now, Mabel was much bigger and Dipper floated with his legs crossed.

"I think I'm supposed to say sorry about earlier today." Dipper mumbled.

"I won't say it's fine Dip." Mabel responded with a soft smile, "Because it's not. But I will remind you how much I love you."

Dipper shrugged, shoulders and wings rising and falling. He let out a huff.

"What?"

"You're just really special, Mabel." He answered. She could tell this was Dipper, as human as he could be, speaking when he used her real name – not her title. "Anyone else would have given up on me."

"You're my brother."

 **"It's not that simple!"** He bit out, **"You've accepted me. A demon. You know there's depravity in me and you still let me in your life, your husband's life, your kids' lives. And I screw up all the time!"**

She wrapped her arms around him, squeezing even as blue sparks danced over her sweater. But she felt the wounds from earlier close. Felt hot, golden droplets soak into the wool.

"Hugs fix everything." She whispered into his suit jacket.

Dipper sighed, "No they don't, Mabel. They don't fix the fact that I can only do so much of this happy family thing before I lose it. I can only go so long without razing the world to the ground. That I've seen futures and dimensions so awful I don't see the point of balance, and chaos makes more sense. That it's been over four hours since I've killed something and it's like an itch I can't scratch."

She squeezed him tighter.

"You don't understand."

Mabel let him go to look him in the eyes. Crescents of molten gold met hers and stared into her soul, his soul. He didn't look away. Whatever he saw there only made him more miserable. And he didn't look away.

"I don't understand. And Dipper, I've tried. But in the end, what matters is that I love you. And I trust you."

His form flickered. A summons. With the risen, full moon, midnight rituals were beginning. She grabbed his hand, this time, careful of his claws.

"I'm coming with you."

A grateful smile, no teeth or malice, graced his features. A human and a demon, hand in hand, disappeared from the rooftop of the Shack. Echoing in her mind, like a broken record player, but infinitely softer, Dipper's answer resounded, "I trust you. And I love you. Mabel. I trust you…"

Soon, it was eclipsed by manic laughter, roaring blue fire, screams of mortal peril. And the scent of blood wafted on the stale cavern air, bringing back memories as scents often do. Of too many deaths all brought about by her dear little brother, the demon.

* * *

When Mabel was twenty, she was stabbed in the heart. Not in the figurative sense. In the literal "there is a ceremonial blade sticking through my chest" sense. It was like nothing she'd ever experienced before. The knife was ripped free, trailing beads of ruby that splattered over a circle of chalk. Her heart traitorously pumped her life through the opening, crimson rivers spilling over everything as she collapsed to the ground. Her fingers twitched weakly, scratching at runes.

Then darkness. In her final moments, there was blue fire and proffered hand. She took it. She would do her best replace what her brother had lost. A soul.

Fin

* * *

 _This is written for an AU of Transcendence AU. I have been informed that it is known as the 'Drift AU', where Dipper isn't naturally visible to Mabel. As a result, he spends two years growing powerful enough to become corporeal and prove that he is still alive. In that time, he has to figure a lot of the demon stuff out on his own and he doesn't have Mabel to be his moral compass. He ends up becoming more demon-like sooner rather than later._

 _A few headcanons to go with this since I don't remember the AU overview being super exhaustive: 1) Dipper prefers to use his title, Mabel's title, and the triplets' true names (given that they aren't in public, but it also doesn't mean he's constantly ordering them around), 2) Given his lack of ability to human, he wouldn't have the savvy to rename Forrest to Hank, so that name stayed, 3) Dipper only accepts legitimate blood sacrifices, 4) He rarely, if ever, makes deals that put himself at a disadvantage (even with Mabel), 5) He's more detached from the family than in the main AU, and 6) Dipper becomes a lot more powerful a lot faster because of his lack of regard for human life_

 _Mods, I hope I didn't screw anything up. I really liked this idea when it was presented. And it's a good excuse to write really REALLY vicious Dipper, which I cannot pass up. Unfortunately, my story didn't turn out that way D:_

 _Oh well! Hope you enjoy!_


End file.
